Fixed bed gasifiers, such as fixed bed dry bottom gasifiers, are also known as moving bed gasifiers or moving bed dry ash gasifiers.
Fixed bed jacketed gasifiers, such as Sasol-Lurgi fixed bed dry bottom gasifiers are being used commercially to gasify carbonaceous material such as coal to produce raw synthesis gas. Such a jacketed gasifier comprises an outer shell or pressure vessel and an inner thermal lining or jacket, which between them define an annulus or jacket space. In use, boiler feed water circulates through the annulus or space or cavity between the jacket and the outer shell by thermosyphon effect, producing saturated steam as a result of heat transfer through the jacket driven by the heat generated through the gasification process occurring inside the gasifier. The inner thermal lining or jacket is subjected to loading and stress as a result of external pressure (in use, the pressure in the annulus or jacket space is typically higher than the gasifier operating pressure), residual installation stresses, thermal fatigue, thermal expansion, clinker crushing and localised hot spots. As a result, the outer shell typically outlasts the jacket and it becomes necessary from time to time to replace the jacket, or at least a cylindrical wall thereof between top and bottom end components. Typically, the annulus or jacket space is inaccessible from outside the gasifier, i.e. welding of jacket components is only possible from inside the gasifier. This invention thus provides, inter alia, a method of constructing an inner thermal lining of a jacketed gasifier, which method can be used to replace the jacket, or portions of the jacket, of a jacketed gasifier.